Coconut water has exploded in popularity as claims of its being as good as or better than sports drinks at hydrating and replenishing electrolyte levels have been tossed around. But now those claims are being called into question. A 2011 report by CNN states that of the three most popular U.S. coconut water drinks—O.N.E., Vito Coco, and Zico— only Zico lived up to its claims of boosting electrolytes. The others were found to have 82% lower sodium and 35% lower magnesium levels than those stated on the products’ labels.

As of this writing, coconut water represents a $200 million dollar industry. As we reported last December, many celebrities have been shown drinking the various brands of coconut water, and many people have been trying it as an alternative to calorie-laden sports drinks. But according to the CNN report, coconut water may not be the appropriate choice for refueling after exercise. In fact, it turns out that ordinary water is usually the best choice as an after workout drink. Unless you workout over 90 minutes, or under strenuous conditions, electrolyte levels don’t fall very much.

So another trend may be losing the wind in its sails. Although coconut water by itself may not be as good at replenishing electrolytes as sports drinks, if it is enriched with sodium, coconut water may be an appropriate choice for after workout refreshment.